1) Well developed brain.
2) Brain is covered with cranium.
3) Notochord, forms on the dorsal side of the primitive gut in the early embryo.
4) Pharyngeal slits connect the pharynx that links the mouth cavity and the esophagus, with the outside.
5) Partially open circulatory system.
6) Two pairs of appendages.
7) The endoskeleton of most vertebrates is made of cartilage or bone.
8) Collagen is present in in a matrix of fibers to provide flexibility.
9) The first vertebrates evolved in the oceans about 470 million years ago. They were jawless fishes with a single caudal fin.
10) Have heart and a closed circulatory system.
11) Circulatory and excretory functions are markedly different from other animals.
12) Reproduction normally sexual and gonochoristic.
13) Unisexual, gonad only one pair.